Technetium-sulfur colloid.

The chemistry of the technetium-sulfur colloid produced by the reaction of sodium thiosulfate with acid was investigated. A commercial kit was duplicated, and analyses of elemental sulfur, bisulfite and residual thiosulfate were carried out. The colloidal dispersions were filtered through Nuclepore graded membranes, and the percentages of sulfur and of 99mTc in the various filtrates were determined. In all cases--with varying acid, thiosulfate and time of incubation--there was a rough agreement between the two percentages for particles 0.4 micron in diameter or more. However, for small particles (less than 0.1 micron) there was virtually no sulfur, but there was an appreciable percentage of technetium. It was concluded that the technetium sulfide nuclei formed first, and that the supersaturated sulfur deposited in part on them and in part on its own nuclei. It was found that raising the pH of the preparation to weakly alkaline values and reheating the solution dissolved most of the deposited sulfur by the reaction with sulfite to form thiosulfate, leaving much smaller, virtually sulfur-free technetium sulfide particles. Such a preparation was found to be as efficient as the technetium-antimony sulfide colloid for lymphograms in dogs. Potassium trithionate, K2S3O6, used in place of sodium thiosulfate, produced small Tc-S colloid particles with less sulfur than the conventional thiosulfate-acid system.

The labeling of high affinity sites of antibodies with 99mTc.

Labeling of F(ab')2 with 99mTc was investigated. The best labeling procedure for F(ab')2 was then applied to IgG and Fab. Stannous ion was used as the reducing agent for 99mTcO-4 and free DTPA was used as a competing reagent to prevent colloid formation and loosely bound 99mTc. The competition reactions revealed two 99mTc binding sites for F(ab')2 and IgG. One is a high capacity, low affinity site. This accounts for 76 and 84% of total IgG and F(ab')2 binding sites. The labeling of these sites can be prevented if the antibody is labeled in the presence of free DTPA. The second site is a low capacity, high affinity site. The labeling of these sites cannot be prevented by free DTPA. Fab, unlike IgG and F(ab')2, does not have an appreciable percentage of high affinity sites. The determination of sulfhydryl groups using Ellman's reagent indicates the production of 5.5, 4.2 and 0.9 sulfhydryl groups when IgG, F(ab')2 and Fab were exposed to 56 micrograms/mL SnCl2 X 2H2O. These sulfhydryl groups may be the source of the high affinity binding. Biodistribution in mice for 99mTc labeled F(ab')2 and F(ab')2-DTPA, both prepared in the presence of excess free DTPA, was similar to that of F(ab')2-DTPA-111In.

Neonatal methadone withdrawal. Effect of two treatment regimens.

Thirty-one infants exposed to methadone in utero who required pharmacologic treatment for withdrawal symptoms were randomly assigned to a paregoric or phenobarbital treatment group. Seven infants had symptoms too mild to require treatment. Respiratory rate, blood pH, PCO2, systolic BP, and serum thyroxine concentrations were measured on the 4th, 7th, and 14th days of life. Platelet counts were performed on the seventh and 14th days of life, and urinary catecholamine excretion was measured on the sixth day of life. Rates of weight gain were recorded during the second and third weeks of life. With the exception of a slightly higher blood PCO2 level in the phenobarbital-treated infants on day 7, no significant intergroup differences were observed in the treated infants. Paregoric-treated infants required a significantly longer period of treatment than phenobarbital-treated infants (22 v 17 days). This may have been due, at least in part, to the prolonged half-life and relatively high blood levels of phenobarbital present after cessation of therapy.